Tool having multi-speed compound planetary transmission

ABSTRACT

A tool having a housing assembly, which defines a handle, a motor assembly, a trigger assembly, a spindle and a transmission assembly. The motor assembly is received in the housing assembly and has an output shaft. The trigger assembly is coupled to the housing assembly and is configured for use in actuating the motor assembly. The transmission assembly transmits rotary power between the output shaft of the motor assembly and the spindle. The transmission assembly includes a planetary stage with an input sun gear, an output planet carrier and a compound planet gear having a first planet gear and a second planet gear coupled together for common rotation on the output planet carrier. The planetary stage is selectively operable in a first gear reduction and a second, relatively lower gear reduction in which the compound planet gear cooperates to produce at least one intermediate gear reduction within the planetary stage.

INTRODUCTION

The present invention generally relates to a tool that has a multi-speedcompound planetary transmission.

Modernly, manufacturers of power tools have introduced power tools thathave variable speed motors in an attempt to permit the users of thesetools with sufficient control over the output speed of the tool so as topermit them to perform diverse operations without resort to additional,specialized tools. Many of the tools that are commercially availableinclude a three-stage, two-speed transmission that permits even greatercontrol over speeds of these tools.

Typically available transmission arrangements have lacked a transmissionarrangement that could produce a wide range of output speeds and torquesthat would permit the tool to perform diverse operations such asdrilling holes with a large diameter hole saw, installing drywall screwsor large diameter lag screws, and performing high-speed drillingoperations. The single or dual speed transmissions that were generallyemployed in these tools typically did not have sufficient speed reducingcapacity to permit these transmissions to be diversely employed asconfiguring these tools for high torque operations tended to impairtheir high speed performance. Furthermore, the rechargeable batteriesthat were employed in many of the early cordless rotary power tools werenot well suited for use in low-speed, high torque operations due to theamount of energy that is consumed and the rate with which the energy isconsumed by the power tool during such operations. Consequently,consumers were often forced to purchase two different rotary powertools, a medium-duty tool for “standard” applications such as drillingand fastening, and a heavy-duty tool having a low-speed, high torqueoutput for more demanding tasks.

With the advent of the modern high capacity, high voltage battery, it isnow possible to meet the energy demands of a power tool that is used inlow-speed, high torque operations. There remains, however, a need in theart for a power tool transmission having a relatively large range in itsspeed reducing capacity.

SUMMARY

This section provides a general summary of some aspects of the presentdisclosure and is not a comprehensive listing or detailing of either thefull scope of the disclosure or all of the features described therein.

The present teachings provide a tool having a housing assembly, a motorassembly, a trigger assembly, a spindle and a transmission assembly. Thehousing assembly defines a handle. The motor assembly is received in thehousing assembly and has an output shaft. The trigger assembly iscoupled to the housing assembly and is configured for use in actuatingthe motor assembly. The transmission assembly transmits rotary powerbetween the output shaft of the motor assembly and the spindle.

In one form, the present teachings provide that the transmissionassembly includes a planetary stage with an input sun gear, an outputplanet carrier and a compound planet gear having a first planet gear anda second planet gear coupled together for common rotation on the outputplanet carrier. The planetary stage is selectively operable in a firstgear reduction and a second, relatively lower gear reduction in whichthe compound planet gear cooperates to produce at least one intermediategear reduction within the planetary stage.

In another form, the present teachings provide that the transmissionassembly includes a gearset portion with a planet carrier, an input sungear, and at least one compound planet gear supported for rotation bythe planet carrier. The planet carrier is an output member of thegearset portion. Each compound planet gear has first and second planetgears that are coupled to one another for common rotation. The firstplanet gear has a pitch diameter that is different from a pitch diameterof the second planet gear. The gearset portion is operable in a firstmode which provides a first gear reduction ratio and a second mode thatprovides a second gear reduction ratio that is different than the firstgear reduction ratio. At least one intermediate gear reduction isprovided within an axial length of the planet carrier when the gearsetportion is operated in the second mode.

In still another form, the present teachings provide that thetransmission assembly includes a gearset portion with a planet carrier,an input sun gear, a compound sun gear, a first planet gear, a secondplanet gear, a third planet gear, and a plurality of ring gears. Thecompound sun gear includes a first intermediate sun gear and a secondintermediate sun gear that are coupled to one another for commonrotation. The first, second and third planet gears are rotatablydisposed on the planet carrier. The second planet gear is coupled to thefirst planet gear for rotation therewith. The first planet gear ismeshingly engaged with the input sun gear. The second planet gear ismeshingly engaged with the first intermediate sun gear. The third planetgear is meshingly engaged with the second intermediate sun gear. Theplurality of ring gears include a first ring gear, which is meshinglyengaged to one of the first, second and third planet gears, and a secondring gear that is meshingly engaged to a different one of the first,second and third planet gears. The gearset portion is operable in afirst mode in which the first ring gear is maintained in a non-rotatingcondition relative to the housing assembly and the second ring gear isrotatable relative to the housing assembly. The gearset portion isoperable in a second mode in which the second ring gear is maintained ina non-rotating condition relative to the housing assembly and the firstring gear is rotatable relative to the housing assembly.

In yet another form, the present teachings provide that the transmissionassembly includes a planetary stage with an input sun gear, an outputplanet carrier and a compound planet gear having a first planet gear anda second planet gear coupled together for common rotation on the outputplanet carrier. The planetary stage is selectively operable in a firstgear reduction and a second, relatively lower gear reduction in whichthe compound planet gear cooperates to produce at least one intermediategear reduction within the planetary stage.

Further areas of applicability will become apparent from the descriptionprovided herein. It should be understood that the description andspecific examples in this summary are intended for purposes ofillustration only and are not intended to limit the scope of the presentdisclosure, its application and/or uses in any way.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings described herein are for illustrative purposes only and arenot intended to limit the scope of the present disclosure in any way.The drawings are illustrative of selected teachings of the presentdisclosure and do not illustrate all possible implementations. Similaror identical elements are given consistent identifying numeralsthroughout the various figures.

FIG. 1 is a side elevation view of an exemplary tool constructed inaccordance with the teachings of the present disclosure;

FIG. 2 is an exploded perspective view of the tool of FIG. 1;

FIG. 3 is a longitudinal section view of a portion of the tool of FIG.1;

FIG. 4 is an enlarged portion of FIG. 3, illustrating a first gearsetportion operating in a fourth mode;

FIG. 5 is a view similar to that of FIG. 4 but depicting the firstgearset portion operating in a second mode;

FIG. 6 is a view similar to that of FIG. 4 but depicting the firstgearset portion operating in a first mode;

FIG. 7 is a longitudinal section view of a portion of another exemplarytool constructed in accordance with the teachings of the presentdisclosure;

FIGS. 8, 9 and 10 are longitudinal section views of a portion of thetool of FIG. 7, depicting a gearset portion of the tool as operating infirst, second and fourth modes, respectively;

FIG. 11 is a longitudinal section view of a portion of another exemplarytool constructed in accordance with the teachings of the presentdisclosure;

FIG. 11A is a longitudinal section view of a portion of a furtherexemplary tool constructed in accordance with the teachings of thepresent disclosure;

FIG. 11B is a longitudinal section view of a portion of still anotherexemplary tool constructed in accordance with the teachings of thepresent disclosure;

FIGS. 12, 13, 14, 15, 16 and 17 are longitudinal section views of aportion of the tool of FIG. 11, depicting a gearset portion of the toolas operating in sixth, fifth, fourth, third, second and first modes,respectively;

FIG. 18 is a longitudinal section view of a portion of another exemplarytool constructed in accordance with the teachings of the presentdisclosure;

FIG. 19 is a longitudinal section view of a portion of another exemplarytool constructed in accordance with the teachings of the presentdisclosure;

FIGS. 20, 21 and 22 are longitudinal section views of a portion of thetool of FIG. 19, depicting a gearset portion of the tool as operating infirst, second and third modes, respectively; and

FIG. 23 is a longitudinal section view of a portion of another exemplarytool constructed in accordance with the teachings of the presentdisclosure.

Corresponding reference numerals indicate corresponding parts throughoutthe several views of the drawings.

DETAILED DESCRIPTION OF THE VARIOUS EMBODIMENTS

With reference to FIGS. 1 and 2, an exemplary tool constructed inaccordance with the teachings of the present disclosure is generallyindicated by reference numeral 10. The tool 10 can include a housingassembly 12, a motor assembly 14, a trigger assembly 16, a transmissionassembly 18, a clutch assembly 20 and an output spindle 22.

The housing assembly 12 can comprise a pair of handle housing shells 30and a gear case 32 that can be removably coupled to the handle housingshells 30 via a plurality of threaded fasteners (not shown). The handlehousing shells 30 can cooperate to define a handle 36, a trigger mount38, and a cavity 40 into which the motor assembly 14 can be received.

The motor assembly 14 and the trigger assembly 16 can be conventional intheir construction and operation. In brief, the motor assembly 14 caninclude an output shaft 46 that can provide a rotary input (torque) tothe transmission assembly 18, while the trigger assembly 16 can bemounted to the trigger mount 38 and employed to selectively couple themotor assembly 14 to a source of electrical power, such as a batterypack 48. In the example provided, the trigger assembly 16 includes atrigger 50, a trigger switch 52, and a reversible variable speedcontroller 54, but it will be appreciated that various other types oftrigger assemblies could be substituted for the particular triggerassembly that is shown in the drawings and described herein.

The transmission assembly 18 can be configured to transmit rotary powerbetween the motor assembly 14 and the output spindle 22 and can includea reduction gearset 60 and a speed change mechanism 62.

With reference to FIGS. 2 through 4, the reduction gearset 60 cancomprise a first planetary stage or gearset portion 70, which receivesrotary power from the motor assembly 14, and a second planetary stage orgearset portion 72 that receives rotary power from the first gearsetportion 70 and transmits rotary power to the output spindle 22.

The first gearset portion 70 can comprise a first or output planetcarrier 80, a first or input sun gear 82, a second sun gear 84, a thirdsun gear 86, a first planet gear 88, a second planet gear 90, a thirdplanet gear 92, a fourth planet gear 94, a first ring gear 96, a secondring gear 98, and a third ring gear 100.

The first planet carrier 80 can comprise a carrier body 104 and aplurality of carrier pins 106. In the example provided, the carrier body104 comprises a rear plate member 110 and a front plate member 112, andthe opposite ends of the carrier pins 106 can be fixedly mounted to therear and front plate members 110 and 112 to axially space the rear platemember 110 apart from the front plate member 112. The first, second,third and fourth planet gears 88, 90, 92 and 94 can be rotatably mountedon the carrier pins 106. In the example provided, one of each of thefirst, second, third and fourth planet gears 88, 90, 92 and 94 isrotatably received on each of the carrier pins 106.

The first sun gear 82 can be coupled to the output shaft 46 of the motorassembly 14 for rotation therewith. Teeth of the first sun gear 82 canbe meshingly engaged to teeth of the first planet gear 88, which in turncan mesh with teeth of the first ring gear 96. The second sun gear 84can be rotatable independently of the output shaft 46, the first sungear 82 and/or the first planet carrier 80. In the example provided, thesecond sun gear 84 is separate and axially offset from the first sungear 82 and is maintained in a position that is concentric about alongitudinal axis of the first gearset portion 70 via the second planetgears 90. It will be appreciated, however, that the output shaft 46could be somewhat longer than that which is shown in FIGS. 2-4 and thatthe second sun gear 84 could be rotatably disposed on the output shaft46. It will also be appreciated that another structure, such as thefirst sun gear 82 or the planet carrier 80, could include a shaft ontowhich the second sun gear 84 and/or the third sun gear 86 could berotatably disposed. Teeth of the second sun gear 84 can be meshinglyengaged to teeth of the second planet gear 90, which in turn can meshwith teeth of the second ring gear 98. Each of the second planet gears90 can be coupled to an associated one of the first planet gears 88 forcommon rotation about an associated one of the carrier pins 106. In theexample provided, each pair of first and second planet gears 88 and 90are unitarily and integrally formed (e.g., compressed and sinteredpowdered metal) and may be collectively referred to as a first compoundplanet gear 120. The third sun gear 86 can be coupled to the second sungear 84 for common rotation. In the particular example provided, thesecond and third sun gears 84 and 86 are unitarily and integrally formed(e.g., compressed and sintered powdered metal) and may be collectivelyreferred to as a first compound sun gear 124. Teeth of the third sungear 86 can be meshingly engaged to teeth of the fourth planet gear 94.Each of the third planet gears 92 can be coupled to an associated one ofthe fourth planet gears 94 for common rotation about an associated oneof the carrier pins 106. In the example provided, each pair of third andfourth planet gears 92 and 94 are unitarily and integrally formed (e.g.,compressed and sintered powdered metal) and may be collectively referredto as a second compound planet gear 128. Teeth of the third planet gears92 can meshingly engage teeth of the third ring gear 100. If desired, athrust washer TW1 can be disposed between the first and second compoundgears 120 and 128.

Each of the first, second and third ring gears 96, 98 and 100 can have aplurality of locking teeth 130 that can be disposed about their outercircumferential surfaces.

The second gearset portion 72 can comprise a planet carrier 134, a sungear 136, a plurality of planet gears 138 and a ring gear 140. Theplanet carrier 134 can comprise a carrier body 144 and a plurality ofcarrier pins 146. The carrier body 144 can comprise a rear plate member148 and a front plate member 150, and the opposite ends of the carrierpins 146 can be fixedly mounted to the rear and front plate members 148and 150 to axially space the rear plate member 148 apart from the frontplate member 150. Each of the planet gears 138 can be rotatably receivedon an associated one of the carrier pins 146 and can be meshinglyengaged with teeth of the sun gear 136 and teeth of the ring gear 140.The ring gear 140 can be rotatably received in the gear case 32.

The speed change mechanism 62 can comprise a movable member 160 and aspeed selector switch assembly 162. In the example provided, the movablemember 160 is an annular collar that is mounted concentrically about thefirst gearset portion 70 and which has internal teeth 166 that areconfigured to engage the locking teeth 130 on the first, second andthird ring gears 96, 98 and 100. The speed selector switch assembly 162can comprise a speed selector switch 170, one or more rails 172, a firstbiasing spring 174, a second biasing spring 176. The speed selectorswitch 170 can be slidably mounted to the housing assembly 12 and can beconfigured to receive a manual switching input from the user of the tool10. The speed selector switch 170 can be translated between a firstswitch position, a second switch position and a third switch position inthe particular example provided. The rails 172 can be fixedly coupled tothe movable member 160 and slidably coupled to the speed selector switch170 such that the movable member 160 can translate relative to the speedselector switch 170 and the first gearset portion 70. The first andsecond biasing springs 174 and 176 can bias the movable member 160 intoa neutral position that corresponds to a position of the speed selectorswitch 170. The first and second biasing springs 174 and 176, however,permit the movable member 160 to be moved relative to the speed selectorswitch 170 in opposite axial directions.

Placement of the speed selector switch 170 in the first switch positionpositions the movable member 160 in a first position in which theinternal teeth 166 of the movable member 160 are engaged with thelocking teeth 130 of the first ring gear 96 such that the first gearsetportion 70 operates in the first mode (i.e., a first overall speedreduction ratio). Movement of the speed selector switch 170 from thefirst switch position to the second switch position positions themovable member 160 in a second position in which the internal teeth 166of the movable member 160 are engaged with the locking teeth 130 of thesecond ring gear 98 such that the first gearset portion 70 operates inthe second mode (i.e., a second overall speed reduction ratio). Movementof the speed selector switch 170 from the second switch position to thethird switch position positions the movable member 160 in a thirdposition in which the internal teeth 166 of the movable member 160 areengaged with the locking teeth 130 of the third ring gear 100 such thatthe first gearset portion 70 operates in the third mode (i.e., a thirdoverall speed reduction ratio).

If the internal teeth 166 of the movable member 160 are not aligned withthe locking teeth of the second ring gear 98 or third ring gear 100 whenthe speed selector switch 170 is moved from the first switch position tothe second switch position or from the second switch position to thethird switch position, the first biasing spring 174 can compress topermit the speed selector switch 170 to move relative to the movablemember 160. Similarly, if the internal teeth 166 of the movable member160 are not aligned with the locking teeth of the second ring gear 98 orthe first ring gear 96 when the speed selector switch is moved from thethird switch position to the second switch position or from the secondswitch position to the first switch position, the second biasing spring176 can compress to permit the speed selector switch 170 to moverelative to the movable member 160. In this way, the user may completethe movement of the speed selector switch 170 (to a desired switchposition) and the first and second biasing springs 174 and 176 can exerta force onto the movable member 160 to axially translate the movablemember 160 (to thereby change the mode in which the first gearsetportion 70 operates) when the internal teeth 166 are in alignment withthe locking teeth 130 on the associated one of the first, second andthird ring gears 96, 98 and 100.

The clutch assembly 20 can be a conventional clutch assembly that can beconfigured to limit the transmission of torque from the transmissionassembly 18 to the output spindle 22. In the particular exampleprovided, the clutch assembly 20 comprises a plurality of clutch pins182, a clutch spring 186 and an adjustment nut 188 that is threadablymounted to a threaded member 190 that is non-rotatably but axiallyslidably mounted to the gear case 32. Each of the clutch pins 182 can bereceived through a corresponding pin hole 194 in the gear case 32. Theclutch pins 182 can abut the ring gear 140 and can abut the clutchspring 186 on a side opposite the ring gear 140. The clutch spring 186can be compressed between the clutch pins 182 and the adjustment nut 188and can apply a force to the clutch pins 182 that resists rotation ofthe ring gear 140. The adjustment nut 188 is threaded to the threadedmember 190 on the clutch housing 180 to permit the force that is exertedby the clutch spring 186 onto the clutch pins 182 to be selectivelyadjusted.

The output spindle 22 can be coupled to the planet carrier 134 forrotation therewith, but in the particular example provided, aconventional spindle lock assembly 198 is disposed between the planetcarrier 134. As those of ordinary skill in the art will appreciate, thespindle lock assembly 198 is configured to permit the planet carrier 134to drive the output spindle 22 and to inhibit rotation of the outputspindle 22 that would tend to drive the planet carrier 134.

With reference to FIG. 4, positioning of the speed selector switch 170(FIG. 3) in the third switch position positions the movable member 160in engagement with the third ring gear 100 such that the third ring gear100 is nonrotatably coupled to the housing assembly 12. Rotary poweroutput from the motor assembly 14 is transmitted from the output shaft46 to the input sun gear 82. Rotation of the input sun gear 82 causescorresponding rotation of the first planet gears 88 due to the meshingengagement of the teeth of the first planet gears 88 with the teeth ofthe input sun gear 82. As the second planet gears 90 are coupled to thefirst planet gears 88 for common rotation and as the teeth of the secondplanet gears 90 are meshingly engaged to the teeth of the second sungear 84, rotation of the second planet gears 90 causes correspondingrotation of the second sun gear 84. It will be appreciated that sincethe pitch diameter of the second planet gears 90 is smaller than thepitch diameter of the first planet gears 88, and since the pitchdiameter of the second sun gear 84 is larger than the pitch diameter ofthe first sun gear 82, the first compound planet gear 120 cooperates toproduce a first intermediate gear reduction within the first gearsetportion 70. Since the third sun gear 86 is coupled to the second sungear for common rotation, and since the teeth of the fourth planet gears94 are meshed with the teeth of the third sun gear 86, rotation of thesecond sun gear 84 causes corresponding rotation of the fourth planetgears 94. It will be appreciated that since the pitch diameter of thethird sun gear 86 is smaller than the pitch diameter of the second sungear 84, and since the pitch diameter of the fourth planet gears 94 islarger than the pitch diameter of the second planet gears 90, the firstcompound sun gear 124 cooperates to produce a second intermediate gearreduction within the first gearset portion 70. It will be furtherappreciated that because the third planet gears 92 are coupled to thefourth planet gears 94 for common rotation, the third planet gears 92will drive the planet carrier 80 such that the first gearset portion 70operates in fourth overall speed reduction ratio. It will be appreciatedthat any ring gears in the first gearset portion 70 that arenon-rotatably coupled to the housing assembly 12 (i.e., via the movablemember 160) are rotatable relative to the housing assembly 12.Accordingly, the first and second ring gears 96 and 98 are rotatablerelative to the housing assembly 12 in this mode of operation.

With reference to FIG. 5, positioning of the speed selector switch 170(FIG. 3) in the second switch position positions the movable member 160in engagement with the second ring gear 98 such that the second ringgear 98 is nonrotatably coupled to the housing assembly 12. Rotary poweroutput from the motor assembly 14 is transmitted from the output shaft46 to the input sun gear 82. Rotation of the input sun gear 82 causescorresponding rotation of the first planet gears 88 due to the meshingengagement of the teeth of the first planet gears 88 with the teeth ofthe input sun gear 82. The second planet gears 90, which rotate with thefirst planet gears 88, will drive the planet carrier 80 such that thefirst gearset portion 70 operates in second overall speed reductionratio. It will be appreciated, however, that rotation of the secondplanet gears 90 will also cause corresponding rotation of the firstcompound sun gear 124 and the second compound planet gear 128. Since thethird ring gear 100 is permitted to rotate relative to the housingassembly 12, rotation of the first compound sun gear 124 and the secondcompound planet gear 128 will have only a minor effect on the efficiencyof the first gearset portion 70.

With reference to FIG. 6, positioning of the speed selector switch 170(FIG. 3) in the first switch position positions the movable member 160in engagement with the first ring gear 96 such that the first ring gear96 is nonrotatably coupled to the housing assembly 12. Rotary poweroutput from the motor assembly 14 is transmitted from the output shaft46 to the input sun gear 82. Rotation of the input sun gear 82 causescorresponding rotation of the first planet gears 88, which drives theplanet carrier 80 such that the first gearset portion 70 operates in afirst overall speed reduction ratio. Rotation of the first planet gears88 will cause corresponding rotation of the second planet gears 90 andthat rotation of the second planet gears 90 will also causecorresponding rotation of the first compound sun gear 124 and the secondcompound planet gear 128. Since the second and third ring gears 98 and100 are permitted to rotate relative to the housing assembly 12,rotation of the second planet gear 90, the first compound sun gear 124and the second compound planet gear 128 will have only a minor effect onthe efficiency of the first gearset portion 70.

It will be appreciated that in all modes other than the first mode (inwhich the first planet gears 88 drive the planet carrier 80 such thatthe first gearset portion 70 operates in a first overall speed reductionratio, the first gearset portion 70 operates such that at least oneintermediate gear reduction is provided between the input sun gear 82and the planet gears that drive the planet carrier 80 (i.e., the planetgears that are meshed with the ring gear that is non-rotatably coupledto the housing assembly 12) to thereby provide the first gearset portion70 with an overall gear reduction ratio that is lower than the overallgear reduction ratio when the first gearset portion 70 is operated inthe first mode.

With reference to FIG. 7, another tool constructed in accordance withthe teachings of the present disclosure is generally indicated byreference numeral 10 a. The tool 10 a can be generally similar to thetool 10 of FIG. 1, except that the first gearset portion 70 aadditionally comprises a fourth ring gear 200 that is disposed betweenthe second and third ring gears 98 and 100, the second compound planetgear 128 is flipped in a front-to-back direction and the speed selectorswitch 170 is movable into a fourth switch position to cause the tool 10a to operate in a fourth mode (i.e., a fourth overall speed reductionratio). The fourth ring gear 200 has teeth that are meshed with theteeth of the fourth planet gears 94 and like the first, second and thirdring gears 96, 98 and 100, locking teeth 130 are formed about the outercircumferential surface of the fourth ring gear 200. The speed selectorswitch 170 may be positioned in the first, second or third switchpositions as is shown in FIGS. 8, 9 and 10, respectively, and the tool10 a will operate as described above with the only difference being thatthe fourth ring gear 200 is rotatable relative to the housing assembly12 when the first gearset portion 70 a is operated in these modes.Positioning of the speed selector switch 170 in the fourth switchposition as shown in FIG. 7 positions the movable member 160 inengagement with the fourth ring gear 200 such that the fourth ring gear200 is nonrotatably coupled to the housing assembly 12. Rotary poweroutput from the motor assembly 14 is transmitted from the output shaft46 to the input sun gear 82. Rotation of the input sun gear 82 causescorresponding rotation of the first planet gears 88 due to the meshingengagement of the teeth of the first planet gears 88 with the teeth ofthe input sun gear 82. As the second planet gears 90 are coupled to thefirst planet gears 88 for common rotation and as the teeth of the secondplanet gears 90 are meshingly engaged to the teeth of the second sungear 84, rotation of the second planet gears 90 causes correspondingrotation of the second sun gear 84. It will be appreciated that sincethe pitch diameter of the second planet gears 90 is smaller than thepitch diameter of the first planet gears 88, and since the pitchdiameter of the second sun gear 84 is larger than the pitch diameter ofthe first sun gear 82, the first compound planet gear 120 cooperates toproduce a first intermediate gear reduction within the first gearsetportion 70 a. Since the third sun gear 86 is coupled to the second sungear 84 for common rotation, and since the teeth of the fourth planetgears 94 are meshed with the teeth of the third sun gear 86, rotation ofthe second sun gear 84 causes corresponding rotation of the fourthplanet gears 94. It will be appreciated that since the pitch diameter ofthe third sun gear 86 is smaller than the pitch diameter of the secondsun gear 84, and since the pitch diameter of the fourth planet gears 94is larger than the pitch diameter of the second planet gears 90, thefirst compound sun gear 124 cooperates to produce a second intermediategear reduction within the first gearset portion 70 a. The fourth planetgears 92 will drive the planet carrier 80 such that the first gearsetportion 70 a operates in a fourth overall speed reduction ratio that isintermediate the second and third overall speed reduction ratios.

In FIG. 11, another tool constructed in accordance with the teachings ofthe present disclosure is generally indicated by reference numeral 10 b.The tool 10 b is generally similar to the tool 10 a of FIG. 7, exceptthat the first gearset portion 70 b further comprises a fourth sun gear250, a fifth sun gear 252, a fifth planet gear 254, a sixth planet gear256, a fifth ring gear 258 and a sixth ring gear 260, and the speedselector switch 170 is movable into fifth and sixth switch position tocause the tool 10 b to operate in fifth and sixth modes, respectively.The fourth sun gear 250 can be axially spaced apart from the third sungear 86 such that it is not directly coupled to the output shaft 46, thefirst sun gear 82, the first compound sun gear 124 or the first planetcarrier 80. Teeth of the fourth sun gear 250 can be meshingly engaged toteeth of the third planet gears 92. The fourth sun gear 250 can becoupled to the fifth sun gear 252 for common rotation. In the particularexample provided, the fourth and fifth sun gears 250 and 252 areunitarily and integrally formed (e.g., compressed and sintered powderedmetal) and may be collectively referred to as a second compound sun gear264. Teeth of the fifth sun gear 252 can be meshingly engaged to teethof the fifth planet gear 254, which can be meshed with teeth of thefifth ring gear 258. Each of the fifth planet gears 254 can be coupledto an associated one of the sixth planet gears 256 for common rotationabout an associated one of the carrier pins 106. In the exampleprovided, each pair of fifth and sixth planet gears 254 and 256 areunitarily and integrally formed (e.g., compressed and sintered powderedmetal) and may be collectively referred to as a third compound planetgear 266. Teeth of the sixth planet gears 256 can meshingly engage teethof the sixth ring gear 260.

Positioning of the speed selector switch 170 in the sixth switchposition positions the movable member 160 in engagement with the sixthring gear 260 (as shown in FIG. 12) such that the sixth ring gear 260 isnonrotatably coupled to the housing assembly 12. Rotary power outputfrom the motor assembly 14 is transmitted from the output shaft 46 tothe input sun gear 82. Rotation of the input sun gear 82 causescorresponding rotation of the first planet gears 88 due to the meshingengagement of the teeth of the first planet gears 88 with the teeth ofthe input sun gear 82. As the second planet gears 90 are coupled to thefirst planet gears 88 for common rotation and as the teeth of the secondplanet gears 90 are meshingly engaged to the teeth of the second sungear 84, rotation of the second planet gears 90 causes correspondingrotation of the second sun gear 84. It will be appreciated that sincethe pitch diameter of the second planet gears 90 is smaller than thepitch diameter of the first planet gears 88, and since the pitchdiameter of the second sun gear 84 is larger than the pitch diameter ofthe first sun gear 82, the first compound planet gear 120 cooperates toproduce a first intermediate gear reduction within the first gearsetportion 70 b. Since the third sun gear 86 is coupled to the second sungear for common rotation, and since the teeth of the fourth planet gears94 are meshed with the teeth of the third sun gear 86, rotation of thesecond sun gear 84 causes corresponding rotation of the third planetgears 92. It will be appreciated that since the pitch diameter of thethird sun gear 86 is smaller than the pitch diameter of the second sungear 84, and since the pitch diameter of the fourth planet gears 94 islarger than the pitch diameter of the second planet gears 90, the firstcompound sun gear 124 cooperates to produce a second intermediate gearreduction within the first gearset portion 70 b. As the third planetgears 92 are coupled to the fourth planet gears 94 for common rotationand as the teeth of the third planet gears 92 are meshingly engaged tothe teeth of the fourth sun gear 250, rotation of the third planet gears92 causes corresponding rotation of the fourth sun gear 250. It will beappreciated that since the pitch diameter of the third planet gears 92is smaller than the pitch diameter of the third planet gears 92, andsince the pitch diameter of the fourth sun gear 250 is larger than thepitch diameter of the third sun gear 86, the second compound planet gear128 cooperates to produce a third intermediate gear reduction within thefirst gearset portion 70 b. Since the fifth sun gear 252 is coupled tothe fourth sun gear for common rotation, and since the teeth of thefifth planet gears 254 are meshed with the teeth of the fifth sun gear252, rotation of the fourth sun gear 250 causes corresponding rotationof the fifth planet gears 254. It will be appreciated that since thepitch diameter of the fifth sun gear 252 is smaller than the pitchdiameter of the fourth sun gear 250, and since the pitch diameter of thefifth planet gears 254 is larger than the pitch diameter of the thirdplanet gears 92, the second compound sun gear 264 cooperates to producea fourth intermediate gear reduction within the first gearset portion 70b. Because the sixth planet gears 256 are coupled to the fifth planetgears 254 for common rotation, the sixth planet gears 256 will drive theplanet carrier 80 such that the first gearset portion 70 b operates insixth overall speed reduction ratio.

Positioning of the speed selector switch 170 in the fifth switchposition positions the movable member 160 in engagement with the fifthring gear 258 (as shown in FIG. 13) such that the fifth ring gear 258 isnonrotatably coupled to the housing assembly 12. Rotary power outputfrom the motor assembly 14 is transmitted from the output shaft 46 tothe input sun gear 82. Rotation of the input sun gear 82 causescorresponding rotation of the first planet gears 88 due to the meshingengagement of the teeth of the first planet gears 88 with the teeth ofthe input sun gear 82. As the second planet gears 90 are coupled to thefirst planet gears 88 for common rotation and as the teeth of the secondplanet gears 90 are meshingly engaged to the teeth of the second sungear 84, rotation of the second planet gears 90 causes correspondingrotation of the second sun gear 84. It will be appreciated that sincethe pitch diameter of the second planet gears 90 is smaller than thepitch diameter of the first planet gears 88, and since the pitchdiameter of the second sun gear 84 is larger than the pitch diameter ofthe first sun gear 82, the first compound planet gear 120 cooperates toproduce a first intermediate gear reduction within the first gearsetportion 70 b. Since the third sun gear 86 is coupled to the second sungear for common rotation, and since the teeth of the fourth planet gears94 are meshed with the teeth of the third sun gear 86, rotation of thesecond sun gear 84 causes corresponding rotation of the fourth planetgears 94. It will be appreciated that since the pitch diameter of thethird sun gear 86 is smaller than the pitch diameter of the second sungear 84, and since the pitch diameter of the fourth planet gears 94 islarger than the pitch diameter of the second planet gears 90, the firstcompound sun gear 124 cooperates to produce a second intermediate gearreduction within the first gearset portion 70 b. As the third planetgears 92 are coupled to the fourth planet gears 94 for common rotationand as the teeth of the third planet gears 92 are meshingly engaged tothe teeth of the fourth sun gear 250, rotation of the third planet gears92 causes corresponding rotation of the fourth sun gear 250. It will beappreciated that since the pitch diameter of the third planet gears 92is smaller than the pitch diameter of the fourth planet gears 94, andsince the pitch diameter of the fourth sun gear 250 is larger than thepitch diameter of the third sun gear 86, the second compound planet gear128 cooperates to produce a third intermediate gear reduction within thefirst gearset portion 70 b. Since the fifth sun gear 252 is coupled tothe fourth sun gear for common rotation, and since the teeth of thefifth planet gears 254 are meshed with the teeth of the fifth sun gear252, rotation of the fourth sun gear 250 causes corresponding rotationof the fifth planet gears 254. Rotation of the fifth planet gears 254drives the planet carrier 80 such that the first gearset portion 70 boperates in fifth overall speed reduction ratio.

Positioning of the speed selector switch 170 in a fourth switch positionpositions the movable member 160 in engagement with the third ring gear100 (as shown in FIG. 14) such that the third ring gear 100 isnonrotatably coupled to the housing assembly 12. Rotary power outputfrom the motor assembly 14 is transmitted from the output shaft 46 tothe input sun gear 82. Rotation of the input sun gear 82 causescorresponding rotation of the first planet gears 88 due to the meshingengagement of the teeth of the first planet gears 88 with the teeth ofthe input sun gear 82. As the second planet gears 90 are coupled to thefirst planet gears 88 for common rotation and as the teeth of the secondplanet gears 90 are meshingly engaged to the teeth of the second sungear 84, rotation of the second planet gears 90 causes correspondingrotation of the second sun gear 84. It will be appreciated that sincethe pitch diameter of the second planet gears 90 is smaller than thepitch diameter of the first planet gears 88, and since the pitchdiameter of the second sun gear 84 is larger than the pitch diameter ofthe first sun gear 82, the first compound planet gear 120 cooperates toproduce a first intermediate gear reduction within the first gearsetportion 70 b. Since the third sun gear 86 is coupled to the second sungear for common rotation, and since the teeth of the third planet gears92 are meshed with the teeth of the third sun gear 86, rotation of thesecond sun gear 84 causes corresponding rotation of the fourth planetgears 94. It will be appreciated that since the pitch diameter of thethird sun gear 86 is smaller than the pitch diameter of the second sungear 84, and since the pitch diameter of the fourth planet gears 94 islarger than the pitch diameter of the second planet gears 90, the firstcompound sun gear 124 cooperates to produce a second intermediate gearreduction within the first gearset portion 70 b. As the third planetgears 92 are coupled to the fourth planet gears 94 for common rotation,the third planet gears 92 drive the planet carrier 80 such that thefirst gearset portion 70 b operates in a fourth overall speed reductionratio.

Positioning of the speed selector switch 170 in a third switch positionpositions the movable member 160 in engagement with the fourth ring gear200 (as shown in FIG. 15) such that the fourth ring gear 200 isnonrotatably coupled to the housing assembly 12. Rotary power outputfrom the motor assembly 14 is transmitted from the output shaft 46 tothe input sun gear 82. Rotation of the input sun gear 82 causescorresponding rotation of the first planet gears 88 due to the meshingengagement of the teeth of the first planet gears 88 with the teeth ofthe input sun gear 82. As the second planet gears 90 are coupled to thefirst planet gears 88 for common rotation and as the teeth of the secondplanet gears 90 are meshingly engaged to the teeth of the second sungear 84, rotation of the second planet gears 90 causes correspondingrotation of the second sun gear 84. It will be appreciated that sincethe pitch diameter of the second planet gears 90 is smaller than thepitch diameter of the first planet gears 88, and since the pitchdiameter of the second sun gear 84 is larger than the pitch diameter ofthe first sun gear 82, the first compound planet gear 120 cooperates toproduce a first intermediate gear reduction within the first gearsetportion 70 b. Since the third sun gear 86 is coupled to the second sungear for common rotation, and since the teeth of the fourth planet gears94 are meshed with the teeth of the third sun gear 86, rotation of thesecond sun gear 84 causes corresponding rotation of the fourth planetgears 94, which drive the planet carrier 80 such that the first gearsetportion 70 b operates in a third overall speed reduction ratio.

Positioning of the speed selector switch 170 in the second switchposition positions the movable member 160 in engagement with the secondring gear 98 (as shown in FIG. 16) such that the second ring gear 98 isnonrotatably coupled to the housing assembly 12. Rotary power outputfrom the motor assembly 14 is transmitted from the output shaft 46 tothe input sun gear 82. Rotation of the input sun gear 82 causescorresponding rotation of the first planet gears 88 due to the meshingengagement of the teeth of the first planet gears 88 with the teeth ofthe input sun gear 82. As the second planet gears 90 are coupled to thefirst planet gears 88 for common rotation, rotation of the second planetgears 90 drives the planet carrier 80 such that the first gearsetportion 70 b operates in a second overall speed reduction ratio.

Positioning of the speed selector switch 170 in the first switchposition positions the movable member 160 in engagement with the firstring gear 96 (as shown in FIG. 17) such that the first ring gear 96 isnonrotatably coupled to the housing assembly 12. Rotary power outputfrom the motor assembly 14 is transmitted from the output shaft 46 tothe input sun gear 82. Rotation of the input sun gear 82 causescorresponding rotation of the first planet gears 88, which drive theplanet carrier 80 such that the first gearset portion 70 b operates in afirst overall speed reduction ratio.

The examples of FIGS. 11A and 11B are generally similar to the exampleof FIG. 11 except that the first sun gear 82 (FIG. 11) has been omittedand that either the first compound sun gear 124 or the second compoundsun gear 264 is coupled to the output shaft 46 for rotation therewith asshown in FIGS. 11A and 11B, respectively.

With regard to the example of FIG. 11A, the speed selector switch 170can be positioned in the sixth switch position, which positions themovable member 160 in engagement with the ring gear 260 such that thering gear 260 is nonrotatably coupled to the housing assembly 12. Rotarypower output from the motor assembly 14 is transmitted from the outputshaft 46 to the first compound sun gear 124. Rotation of the firstcompound sun gear 124 causes corresponding rotation of the planet gears92 due to the meshing engagement of the teeth of the planet gears 92with the teeth of the sun gear 86. As the planet gears 92 are coupled tothe planet gears 94 for common rotation and as the teeth of the planetgears 92 are meshingly engaged to the teeth of the sun gear 250,rotation of the planet gears 92 causes corresponding rotation of the sungear 250. It will be appreciated that since the pitch diameter of theplanet gears 92 is smaller than the pitch diameter of the planet gears92, and since the pitch diameter of the sun gear 250 is larger than thepitch diameter of the sun gear 86, the second compound planet gear 128cooperates to produce a first intermediate gear reduction within thefirst gearset portion 70 b. Since the sun gear 252 is coupled to the sungear for common rotation, and since the teeth of the planet gears 254are meshed with the teeth of the sun gear 252, rotation of the sun gear250 causes corresponding rotation of the planet gears 254. It will beappreciated that since the pitch diameter of the sun gear 252 is smallerthan the pitch diameter of the sun gear 250, and since the pitchdiameter of the planet gears 254 is larger than the pitch diameter ofthe planet gears 92, the second compound sun gear 264 cooperates toproduce a second intermediate gear reduction within the first gearsetportion 70 b. Because the planet gears 256 are coupled to the planetgears 254 for common rotation, the planet gears 256 will drive theplanet carrier 80 such that the first gearset portion 70 b operates insixth overall speed reduction ratio.

Positioning of the speed selector switch 170 in the fifth switchposition positions the movable member 160 in engagement with the ringgear 258 such that the ring gear 258 is nonrotatably coupled to thehousing assembly 12. Rotary power output from the motor assembly 14 istransmitted from the output shaft 46 to the first compound sun gear 124.Rotation of the first compound sun gear 124 causes correspondingrotation of the planet gears 92 due to the meshing engagement of theteeth of the planet gears 92 with the teeth of the sun gear 86. As theplanet gears 92 are coupled to the planet gears 94 for common rotationand as the teeth of the planet gears 92 are meshingly engaged to theteeth of the sun gear 250, rotation of the planet gears 92 causescorresponding rotation of the sun gear 250. It will be appreciated thatsince the pitch diameter of the planet gears 92 is smaller than thepitch diameter of the planet gears 92, and since the pitch diameter ofthe sun gear 250 is larger than the pitch diameter of the sun gear 86,the second compound planet gear 128 cooperates to produce a firstintermediate gear reduction within the first gearset portion 70 b. Sincethe sun gear 252 is coupled to the sun gear for common rotation, andsince the teeth of the planet gears 254 are meshed with the teeth of thesun gear 252, rotation of the sun gear 250 causes corresponding rotationof the planet gears 254. Rotation of the planet gears 254 drives theplanet carrier 80 such that the first gearset portion 70 b operates infifth overall speed reduction ratio.

Positioning of the speed selector switch 170 in a fourth switch positionpositions the movable member 160 in engagement with the ring gear 100such that the ring gear 100 is nonrotatably coupled to the housingassembly 12. Rotary power output from the motor assembly 14 istransmitted from the output shaft 46 to the first compound sun gear 124.Rotation of the first compound sun gear 124 causes correspondingrotation of the planet gears 92 due to the meshing engagement of theteeth of the planet gears 92 with the teeth of the sun gear 86. As theplanet gears 92 are coupled to the planet gears 94, the planet gears 94drive the planet carrier 80 such that the first gearset portion 70 boperates in a fourth overall speed reduction ratio.

Positioning of the speed selector switch 170 in a third switch positionpositions the movable member 160 in engagement with the ring gear 200such that the ring gear 200 is nonrotatably coupled to the housingassembly 12. Rotary power output from the motor assembly 14 istransmitted from the output shaft 46 to the first compound sun gear 124.Rotation of the first compound sun gear 124 causes correspondingrotation of the planet gears 92 due to the meshing engagement of theteeth of the planet gears 92 with the teeth of the sun gear 86. Theplanet gears 92 drive the planet carrier 80 such that the first gearsetportion 70 b operates in a third overall speed reduction ratio.

Positioning of the speed selector switch 170 in the second switchposition positions the movable member 160 in engagement with the ringgear 98 such that the ring gear 98 is nonrotatably coupled to thehousing assembly 12. Rotary power output from the motor assembly 14 istransmitted from the output shaft 46 to the first compound sun gear 124.Rotation of the first compound sun gear 124 causes correspondingrotation of the planet gears 90 due to the meshing engagement of theteeth of the planet gears 90 with the teeth of the sun gear 84. Theplanet gears 90 drive the planet carrier 80 such that the first gearsetportion 70 b operates in a second overall speed reduction ratio.

Positioning of the speed selector switch 170 in the first switchposition positions the movable member 160 in engagement with the ringgear 96 (as shown in FIG. 17) such that the ring gear 96 is nonrotatablycoupled to the housing assembly 12. Rotation of the first compound sungear 124 causes corresponding rotation of the planet gears 90 due to themeshing engagement of the teeth of the planet gears 90 with the teeth ofthe sun gear 84. As the planet gears 88 are coupled to the planet gears90 for rotation therewith, the planet gears 88 drive the planet carrier80 such that the first gearset portion 70 b operates in a first overallspeed reduction ratio.

With regard to the example of FIG. 11B, the speed selector switch 170can be positioned in the sixth switch position, which positions themovable member 160 in engagement with the ring gear 260 such that thering gear 260 is nonrotatably coupled to the housing assembly 12. Rotarypower output from the motor assembly 14 is transmitted from the outputshaft 46 to the second compound sun gear 264. Rotation of the secondcompound sun gear 264 causes corresponding rotation of the planet gears254 due to the meshing engagement of the teeth of the planet gears 254with the teeth of the sun gear 252. As the planet gears 254 are coupledto the planet gears 256 for common rotation and as the teeth of theplanet gears 254 are meshingly engaged to the teeth of the sun gear 252,the planet gears 256 will drive the planet carrier 80 such that thefirst gearset portion 70 b operates in sixth overall speed reductionratio.

Positioning of the speed selector switch 170 in the fifth switchposition positions the movable member 160 in engagement with the ringgear 258 such that the ring gear 258 is nonrotatably coupled to thehousing assembly 12. Rotary power output from the motor assembly 14 istransmitted from the output shaft 46 to the second compound sun gear264. Rotation of the second compound sun gear 264 causes correspondingrotation of the planet gears 254 due to the meshing engagement of theteeth of the planet gears 254 with the teeth of the sun gear 252.Rotation of the planet gears 254 drives the planet carrier 80 such thatthe first gearset portion 70 b operates in fifth overall speed reductionratio.

Positioning of the speed selector switch 170 in a fourth switch positionpositions the movable member 160 in engagement with the ring gear 100such that the ring gear 100 is nonrotatably coupled to the housingassembly 12. Rotary power output from the motor assembly 14 istransmitted from the output shaft 46 to the second compound sun gear264. Rotation of the second compound sun gear 264 causes correspondingrotation of the planet gears 94 due to the meshing engagement of theteeth of the planet gears 94 with the teeth of the sun gear 250.Rotation of the planet gears 94 drives the planet carrier 80 such thatthe first gearset portion 70 b operates in fourth overall speedreduction ratio.

Positioning of the speed selector switch 170 in a third switch positionpositions the movable member 160 in engagement with the ring gear 200such that the ring gear 200 is nonrotatably coupled to the housingassembly 12. Rotary power output from the motor assembly 14 istransmitted from the output shaft 46 to the second compound sun gear264. Rotation of the second compound sun gear 264 causes correspondingrotation of the planet gears 94 due to the meshing engagement of theteeth of the planet gears 94 with the teeth of the sun gear 250. Sincethe planet gears 92 are coupled for rotation with the planet gears 94for common rotation, the planet gears 92 drive the planet carrier 80such that the first gearset portion 70 b operates in a third overallspeed reduction ratio.

Positioning of the speed selector switch 170 in the second switchposition positions the movable member 160 in engagement with the ringgear 98 such that the ring gear 98 is nonrotatably coupled to thehousing assembly 12. Rotary power output from the motor assembly 14 istransmitted from the output shaft 46 to the second compound sun gear264. Rotation of the second compound sun gear 264 causes correspondingrotation of the planet gears 94 due to the meshing engagement of theteeth of the planet gears 94 with the teeth of the sun gear 250. Sincethe planet gears 92 are coupled for rotation with the planet gears 94for common rotation, the planet gears 92 drive sun gear 86. Since thesun gear 84 is coupled for rotation with the sun gear 86, rotation ofthe sun gear 86 causes corresponding rotation of the planet gears 90(due to meshing engagement between the planet gears 90 and the sun gear84). Rotation of the planet gears 90 drives the planet carrier 80 suchthat the first gearset portion 70 b operates in a second overall speedreduction ratio.

Positioning of the speed selector switch 170 in the first switchposition positions the movable member 160 in engagement with the ringgear 96 (as shown in FIG. 17) such that the ring gear 96 is nonrotatablycoupled to the housing assembly 12. Rotary power output from the motorassembly 14 is transmitted from the output shaft 46 to the secondcompound sun gear 264. Rotation of the second compound sun gear 264causes corresponding rotation of the planet gears 94 due to the meshingengagement of the teeth of the planet gears 94 with the teeth of the sungear 250. Since the planet gears 92 are coupled for rotation with theplanet gears 94 for common rotation, the planet gears 92 drive sun gear86. Since the sun gear 84 is coupled for rotation with the sun gear 86,rotation of the sun gear 86 causes corresponding rotation of the planetgears 90 (due to meshing engagement between the planet gears 90 and thesun gear 84). As the planet gears 88 are coupled to the planet gears 90for rotation therewith, rotation of the planet gears drives the planetgears 88, which drive the planet carrier 80 such that the first gearsetportion 70 b operates in a first overall speed reduction ratio.

In FIG. 18, another tool constructed in accordance with the teachings ofthe present disclosure is generally indicated by reference numeral 10 c.The tool 10 c is generally similar to the tool 10 b of FIG. 11, exceptthat the first gearset portion 70 b is configured to output rotary powerdirectly to the output spindle 22 c. In this regard, the planet carrier80 c is modified to work directly with the spindle lock assembly 198 totransmit rotary power to the output spindle 22 c.

In FIG. 19, a further tool constructed in accordance with the teachingsof the present disclosure is generally indicated by reference numeral 10d. The tool 10 d is generally similar to the tool 10 a of FIG. 7, exceptfor the configuration of the first gearset portion and the speedselector switch. More specifically, the first gearset portion 70 d isconfigured such that the first or input sun gear 82 is positionedproximate the front plate member 112 d, the ring gear meshed with thefirst planet gears 88 has been omitted, and the speed selector switch170 is selectively positionable in first, second and third switchpositions.

Positioning of the speed selector switch 170 in the third switchposition (shown in FIG. 20) positions the movable member 160 inengagement with the third ring gear 100 (closest to the motor assembly14 d in this example) such that the third ring gear 100 is nonrotatablycoupled to the housing assembly 12. Rotary power output from the motorassembly 14 d is transmitted from the output shaft 46 d to the input sungear 82. Rotation of the input sun gear 82 causes corresponding rotationof the first planet gears 88 due to the meshing engagement of the teethof the first planet gears 88 with the teeth of the input sun gear 82. Asthe second planet gears 90 are coupled to the first planet gears 88 forcommon rotation and as the teeth of the second planet gears 90 aremeshingly engaged to the teeth of the second sun gear 84, rotation ofthe second planet gears 90 causes corresponding rotation of the secondsun gear 84. It will be appreciated that since the pitch diameter of thesecond planet gears 90 is smaller than the pitch diameter of the firstplanet gears 88, and since the pitch diameter of the second sun gear 84is larger than the pitch diameter of the first sun gear 82, the firstcompound planet gear 120 cooperates to produce a first intermediate gearreduction within the first gearset portion 70 d. Since the third sungear 86 is coupled to the second sun gear for common rotation, and sincethe teeth of the fourth planet gears 94 are meshed with the teeth of thethird sun gear 86, rotation of the second sun gear 84 causescorresponding rotation of the fourth planet gears 94. It will beappreciated that since the pitch diameter of the third sun gear 86 issmaller than the pitch diameter of the second sun gear 84, and since thepitch diameter of the fourth planet gears 94 is larger than the pitchdiameter of the second planet gears 90, the first compound sun gear 124cooperates to produce a second intermediate gear reduction within thefirst gearset portion 70 d. It will be further appreciated that becausethe third planet gears 92 are coupled to the fourth planet gears 94 forcommon rotation, the third planet gears 92 will drive the planet carrier80 such that the first gearset portion 70 d operates in a third overallspeed reduction ratio.

Positioning of the speed selector switch 170 in the second switchposition (shown in FIG. 21) positions the movable member 160 inengagement with the second ring gear 98 such that the second ring gear98 is nonrotatably coupled to the housing assembly 12. Rotary poweroutput from the motor assembly 14 is transmitted from the output shaft46 to the input sun gear 82. Rotation of the input sun gear 82 causescorresponding rotation of the first planet gears 88 due to the meshingengagement of the teeth of the first planet gears 88 with the teeth ofthe input sun gear 82. As the second planet gears 90 are coupled to thefirst planet gears 88 for common rotation and as the teeth of the secondplanet gears 90 are meshingly engaged to the teeth of the second sungear 84, rotation of the second planet gears 90 causes correspondingrotation of the second sun gear 84. It will be appreciated that sincethe pitch diameter of the second planet gears 90 is smaller than thepitch diameter of the first planet gears 88, and since the pitchdiameter of the second sun gear 84 is larger than the pitch diameter ofthe first sun gear 82, the first compound planet gear 120 cooperates toproduce a first intermediate gear reduction within the first gearsetportion 70 d. Since the third sun gear 86 is coupled to the second sungear for common rotation, and since the teeth of the fourth planet gears94 are meshed with the teeth of the third sun gear 86, rotation of thesecond sun gear 84 causes corresponding rotation of the fourth planetgears 94. It will be appreciated that since the pitch diameter of thethird sun gear 86 is smaller than the pitch diameter of the second sungear 84, and since the pitch diameter of the fourth planet gears 94 islarger than the pitch diameter of the second planet gears 90, the firstcompound sun gear 124 cooperates to produce a second intermediate gearreduction within the first gearset portion 70 d. The fourth planet gears94 will drive the planet carrier 80 such that the first gearset portion70 d operates in a second overall speed reduction ratio that isintermediate the first and third overall speed reduction ratios.

Positioning of the speed selector switch 170 in the first switchposition (shown in FIG. 22) positions the movable member 160 inengagement with the first ring gear 96 such that the first ring gear 96is nonrotatably coupled to the housing assembly 12. Rotary power outputfrom the motor assembly 14 is transmitted from the output shaft 46 tothe input sun gear 82. Rotation of the input sun gear 82 causescorresponding rotation of the first planet gears 88 due to the meshingengagement of the teeth of the first planet gears 88 with the teeth ofthe input sun gear 82. The second planet gears 90 will drive the planetcarrier 80 such that the first gearset portion 70 d operates in a firstoverall speed reduction ratio.

With reference to FIG. 23, another tool constructed in accordance withthe teachings of the present disclosure is generally indicated byreference numeral 10 e. The tool 10 e is generally similar to the tool10 d of FIG. 19, except that the second ring gear 98 has been omitted.Accordingly, the tool 10 e has a first gearset portion 70 e that isselectively operable in two overall speed reduction ratios.

It will be appreciated that the above description is merely exemplary innature and is not intended to limit the present disclosure, itsapplication or uses. While specific examples have been described in thespecification and illustrated in the drawings, it will be understood bythose of ordinary skill in the art that various changes may be made andequivalents may be substituted for elements thereof without departingfrom the scope of the present disclosure as defined in the claims.Furthermore, the mixing and matching of features, elements and/orfunctions between various examples is expressly contemplated herein,even if not specifically shown or described, so that one of ordinaryskill in the art would appreciate from this disclosure that features,elements and/or functions of one example may be incorporated intoanother example as appropriate, unless described otherwise, above.Moreover, many modifications may be made to adapt a particular situationor material to the teachings of the present disclosure without departingfrom the essential scope thereof. Therefore, it is intended that thepresent disclosure not be limited to the particular examples illustratedby the drawings and described in the specification as the best modepresently contemplated for carrying out the teachings of the presentdisclosure, but that the scope of the present disclosure will includeany embodiments falling within the foregoing description and theappended claims.

What is claimed is:
 1. A power tool comprising: a housing assemblydefining a handle; a motor assembly received in the housing assembly andhaving an output shaft; a trigger assembly coupled to the housingassembly and configured for use in actuating the motor assembly; aspindle; and a transmission assembly transmitting rotary power betweenthe motor assembly and the spindle, the transmission assembly comprisinga planetary stage with an input sun gear, an output planet carrier, acompound planet gear having a first planet gear and a second planet gearcoupled together for common rotation on the output planet carrier, and athird planet gear also coupled for rotation on the output planetcarrier, wherein the planetary stage is selectively operable in a firstgear reduction, a second, relatively lower gear reduction in which thecompound planet gear cooperates to produce at least one intermediategear reduction within the planetary stage and a third gear reductionthat is different from the first and second gear reductions.
 2. The toolof claim 1, wherein the transmission assembly includes a member that ismovable between a first position and a second position, wherein theplanetary stage operates in the first gear reduction when the member ispositioned in the first position and wherein the planetary stageoperates in the second gear reduction when the member is positioned inthe second position.
 3. The tool of claim 2, wherein the planetary stagefurther comprises a plurality of ring gears and wherein the memberengages a first one of the plurality of ring gears when the member ispositioned in the first position and wherein the member engages a secondone of the plurality of ring gears when the member is positioned in thesecond position.
 4. The tool of claim 3, wherein engagement of themember to any one of the plurality of ring gears nonrotatably couplesthat ring gear to the housing assembly.
 5. The tool of claim 2, whereinthe transmission assembly further comprises a speed selector switch andwherein the member is resiliently coupled to the speed selector switch.6. The tool of claim 5, wherein the member is biased into a neutralposition and is movable relative to the speed selector switch inopposite axial directions.
 7. The power tool of claim 2, wherein themember is moveable to a third position to cause the planetary stage tooperate in the third gear reduction.
 8. The power tool of claim 7,wherein the planetary stage further comprises a first ring gear thatmeshes with the first planet gear, a second ring gear that meshes withthe second planet gear, and a third ring gear that meshes with the thirdring gear, and wherein the member non-rotationally couples the firstring gear to the housing assembly when the member is positioned in thefirst position, non-rotationally couples the second ring gear to thehousing assembly when the member is positioned in the second position,and non-rotationally couples the third ring gear to the housing assemblywhen the member is positioned in the third position.
 9. The tool ofclaim 1, wherein when the planetary stage is operable in the third gearreduction, the first intermediate gear reduction and a secondintermediate gear reduction are produced within the planetary stage. 10.The tool of claim 1, further comprising a clutch for limiting torquetransmitted from the transmission assembly to the spindle.
 11. The toolof claim 1, wherein the input sun gear is directly driven by the outputshaft of the motor assembly.
 12. A power tool comprising: a housingassembly defining a handle; a motor assembly received in the housingassembly and having an output shaft; a trigger assembly coupled to thehousing assembly and configured for use in actuating the motor assembly;a spindle; and a transmission assembly transmitting rotary power betweenthe motor assembly and the spindle, the transmission assembly comprisinga gearset portion with a planet carrier, an input sun gear, at least onecompound planet gear having first and second planet gears coupled to oneanother for common rotation and supported for rotation by the planetcarrier, and a third planet gear also supported for rotation by theplanet carrier, the planet carrier being an output member of the gearsetportion, wherein the first planet gear has a pitch diameter that isdifferent from a pitch diameter of the second planet gear, wherein thegearset portion is operable in a first mode which provides a first gearreduction ratio, a second mode that provides a second gear reductionratio that is different than the first gear reduction ratio, and a thirdmode that provides a third gear reduction ratio that is different fromthe first and second gear reduction ratios, wherein in the second modeat least one intermediate gear reduction is provided within the gearsetportion.
 13. The tool of claim 12, wherein the transmission assemblyincludes a member that is movable between a first position and a secondposition, wherein the planetary stage operates in the first mode whenthe member is positioned in the first position and wherein the planetarystage operates in the second mode when the member is positioned in thesecond position.
 14. The tool of claim 13, wherein the planetary stagefurther comprises a plurality of ring gears and wherein the memberengages a first one of the plurality of ring gears when the member ispositioned in the first position and wherein the member engages a secondone of the plurality of ring gears when the member is positioned in thesecond position.
 15. The tool of claim 14, wherein engagement of themember to any one of the plurality of ring gears nonrotatably couplesthat ring gear to the housing assembly.
 16. The tool of claim 13,wherein the transmission assembly further comprises a speed selectorswitch and wherein the member is resiliently coupled to the speedselector switch.
 17. The tool of claim 16, wherein the member is biasedinto a neutral position wherein the member is biased into a neutralposition and is movable relative to the speed selector switch inopposite axial directions.
 18. The power tool of claim 13, wherein themember is moveable to a third position to cause the planetary stage tooperate in the third mode.
 19. The power tool of claim 18, wherein theplanetary stage further comprises a first ring gear that meshes with thefirst planet gear, a second ring gear that meshes with the second planetgear, and a third ring gear that meshes with the third ring gear, andwherein the member non-rotationally couples the first ring gear to thehousing assembly when the member is positioned in the first position,non-rotationally couples the second ring gear to the housing assemblywhen the member is positioned in the second position, andnon-rotationally couples the third ring gear to the housing assemblywhen the member is positioned in the third position.
 20. The power toolof claim 12, wherein when the planetary stage is operable in the thirdmode, the first intermediate gear reduction and a second intermediategear reduction are produced within the planetary stage.
 21. A power toolcomprising: a housing assembly defining a handle; a motor assemblyreceived in the housing assembly and having an output shaft; a triggerassembly coupled to the housing assembly and configured for use inactuating the motor assembly; a spindle; and a transmission assemblytransmitting rotary power between the motor assembly and the spindle,the transmission assembly comprising a planetary stage with an input sungear, an output planet carrier, a compound planet gear having a firstplanet gear and a second planet gear coupled together for commonrotation on the output planet carrier, and a third planet gear alsocoupled for rotation on the output planet carrier, wherein the planetarystage is selectively operable in a first mode to perform a first speedreduction, in a second mode to perform a second, relatively greaterspeed reduction in which the compound planet gear cooperates to produceat least one intermediate speed reduction within the planetary stage,and in an third mode to perform a third speed reduction that is greaterthan both the first and second speed reductions.
 22. The power tool ofclaim 21, wherein the transmission assembly includes a member that ismovable among a first position, a second position and a third position,wherein the planetary stage operates in the first mode when the memberis positioned in the first position, operates in the second mode whenthe member is positioned in the second position, and operates in thethird mode when the member is positioned in the third position.
 23. Thepower tool of claim 22, wherein the planetary stage further comprises afirst ring gear that meshes with the first planet gear, a second ringgear that meshes with the second planet gear, and a third ring gear thatmeshes with the third ring gear, and wherein the member non-rotationallycouples the first ring gear to the housing assembly when the member ispositioned in the first position, non-rotationally couples the secondring gear to the housing assembly when the member is positioned in thesecond position, and non-rotationally couples the third ring gear to thehousing assembly when the member is positioned in the third position.24. The power tool of claim 21, wherein when the planetary stage isoperable in the third mode, the planetary stage produces the firstintermediate speed reduction and a second intermediate speed reductionwithin the planetary stage.
 25. A power tool comprising: a housingassembly defining a handle; a motor assembly received in the housingassembly and having an output shaft; a trigger assembly coupled to thehousing assembly and configured for use in actuating the motor assembly;a spindle; and a transmission assembly transmitting rotary power betweenthe motor assembly and the spindle, the transmission assembly comprisinga gearset portion with a planet carrier, an input sun gear, a compoundsun gear, a first planet gear, a second planet gear, a third planetgear, and a plurality of ring gears, the compound sun gear comprising afirst intermediate sun gear and a second intermediate sun gear that arecoupled to one another for common rotation, the first, second and thirdplanet gears being rotatably disposed on the planet carrier, the secondplanet gear being coupled to the first planet gear for rotationtherewith, the first planet gear being meshingly engaged with the inputsun gear, the second planet gear being meshingly engaged with the firstintermediate sun gear, and the third planet gear being meshingly engagedwith the second intermediate sun gear, the plurality of ring gearscomprising a first ring gear, which is meshingly engaged to one of thefirst, second and third planet gears, and a second ring gear that ismeshingly engaged to a different one of the first, second and thirdplanet gears, wherein the gearset portion is operable in a first mode inwhich the first ring gear is maintained in a non-rotating conditionrelative to the housing assembly and the second ring gear is rotatablerelative to the housing assembly, and wherein the gearset portion isoperable in a second mode in which the second ring gear is maintained ina non-rotating condition relative to the housing assembly and the firstring gear is rotatable relative to the housing assembly.